Download Top 10 Earthquakes since 1900

… they help tell Earth’s story!
Regents Earth Science
With Ms. Connery
EARTHQUAKE VOCABULARY
earthquake
fault
convergent
divergent
transform (or
transverse)
seismic energy
epicenter
focus
Richter scale
magnitude
Mercalli scale travel time
seismic risk
arrival time
surface waves origin time
body waves
mantle
convection
p-waves
compression plate tectonics
plate
s-waves
boundaries
shear
s-wave shadow earthquake
prediction
zone
What DOES an
EARTH“quake” look likE?
But the local quake MAY
NOT BE the only
problem!
WHY IS IT IMPORTANT
TO UNDERSTAND
EARTHQUAKES?
Do you think we can
predict them?
Where are the
volcanoes and
quakes
happening
today???
Volcanoes
SEISMOLOGY (Earthquakes)
Remember, the
EVIDENCE –
LOCATIONS OF
VOLCANOES AND
EARTHQUAKES CAME FIRST
before plate
boundaries could
be drawn!
Quakes, MOUNTAIN chains, AND
VOLCANOES ARE ALL RELATED!
IT’S ALL ABOUT
earth’s CRUST in
MOTION – PLATE
TECTONICS!!!
Its all
convection
inrelationship
the asthenosphere
Here’s
howabout
scientists
explain the
you observed
(plastic mantle) & earthquake seismic waves prove it!
How does a lava lamp help us
understand plate motion?
How does Mantle convection
cause plate motion?
Mantle convection
causes plate motion!
plate motion & volcanoes
cause stresses to build up in
the rocks.
When the stresses overcome
friction, movement OCCURS
and causes an earthquake!
Its all about convection in the asthenosphere
(plastic mantle) & earthquake seismic waves prove it!
earthquakes
What is an Earthquake?
It’s the SEISMIC
ENERGY that’s
released when the
earth “breaks”
along a fault zone
After
Before
< 1 Sec
How do we describe where
an earthquake occurs In
the lithosphere?
Focus is on the
fault zone where
the earthquake
occurred below
ground
How do we describe where
an earthquake occurs In
the lithosphere?
Be sure you know
the difference!
Epicenter is the
surface location used to
describe where it
happened using latitude
and longitude.
Focus
Earthquakes happen along faults
Divergence (slip fault)
Convergence (thrust fault)
Transverse (transform fault)
Generally they occur
from three types of
fault movement
caused by:
 pulling (extension)
 pushing
(compression)
sliding of the fault
blocks (lateral)
What is an earthquake?
• The fault locations are
somewhat predictable
• BUT exactly where &
when an earthquake will
occur its magnitude are
all unpredictable!
• Just like a pencil!
L –o -n -g -e -r
the distance moved
along the fault
the
bigger
earthquake!
the
Scales used to describe
earthquakes
1. Richter “Magnitude” Scale
• Based on energy released
• Magnitude = X10 for each step
• Energy released about 30x
greater each step
RICHTER SCALE
Largest Earthquakes
since 1900
Scales used to describe
earthquakes
1. Richter “Magnitude” Scale
2. Mercalli Intensity Scale of
“Effects”
• Damage done based on costs
• Useful for insurance
USGS Map of Us seismic risks
earthquakes
An earthquake happens
when the forces that hold
the crust (rock) together
are not as strong as the
forces trying to tear it apart
Just like a pencil!
– When friction “loses” the battle,
movement occurs along the fault
zone
– Seismic energy is released in
waves in 3-D (all directions) when
the earthquake happens
Seismic energy is released in waves
travelling in all directions (3D)
The seismic waves are called:
– Body waves (underground)
• primary seismic waves (p-waves)
• secondary seismic waves (s-waves)
– surface waves (above ground)
Draw isochron maps to see EVIDENCE
that shows p-waves differ from s-waves
What are the
characteristics of the
p and s seismic waves that
give them different speeds?
It’s slinky science time!
P-waves
Primary = p-waves
Compressional waves - similar to the motion of a
slinky.
Particles move in same direction as energy wave
travels
p-waves are fast (4-7 km/sec)
High density material  fast wave speed
p-waves move through solid, liquid, & gas
S-waves
Secondary = s-waves
Shear (transverse) waves – think rope
Particles move perpendicular to the direction the
energy wave is traveling
S-waves slower than p-waves (2-5 km/sec)
High density material  faster wave speed
Only travel through solids (can’t shear liquid or gas)
• EQKE Recording instruments are called
SEISMOGRAPHS (aka SEISMOMETERS)
• “Written” record of an earthquake is called a
SEISMOGRAM
How do we
know the
properties
of Earth’s
layers?
Seismic refraction and
reflection of waves show
us earth has layers with
different properties!
Seismic
Waves!!
http://www.astro.virginia.edu/class/oconnell/astr121/im/seismic-waves-crossec-CM.jpg
… since s-waves don’t make it
through to the other side of
Earth (shadow zone) so there
must be a liquid outer core that
stops them!
http://www.visionlearning.com/library/module_viewer.php?mid=69
EARTHQUAKE
HAPPENS and
energy waves
are released
Seismogram shows
WHEN the SEISMIC waves
arrive at a station!
Faster P-wave arrives at
the seismograph FIRST
P-WAVE
ARRIVAL TIME
EARTHQUAKE
HAPPENS and
energy waves
are released
Slower s-wave arrives at
the seimograph LATER
S-WAVE
ARRIVAL TIME
P-WAVE
ARRIVAL TIME
EARTHQUAKE
HAPPENS and
energy waves
are released
S-WAVE
ARRIVAL TIME
P and s waves
take different
amounts of time
to travel the
same distance
away from an
equake because
they move in
different ways
http://eqseis.geosc.psu.edu/~cammon/QA/wellsNV-21Feb2008.html
PRACTICE KEEPing UP
WITH THE “times” !
ORIGIN TIME
(earthquake happens)
00:00:00
ARRIVAL TIME
(when waves arrive at a seismograph)
TRAVEL TIME
(how long it took waves to get there)
What is a
seismogram?
EARTHQUAKE
(energy waves
are released)
Earthquake
happens at the
TIME of ORIGIN
and waves travel
out FROM FOCUS
Faster P-wave
arrives at the
seismograph FIRST
P-WAVE
ARRIVAL
TIME
Time gap
btw p
and s
Slower s-wave arrives at
the seimograph LATER
S-WAVE
ARRIVAL TIME
Label the slower
wave graph
y axis = how long it took for
the seismic waves to travel
to the seismograph
What is the scale
for travel time?
1 min = 60 sec
60sec/3 = ???
Label the faster
wave graph
20 sec/ block
00:05:20
x axis = how far away
the seismograph is from
the earthquake
What is the
scale for
epicenter
distance?
Why does
the time gap
btw. arrival
of p & s
waves
change?
Practice using the esrt!!
What is a
seismogram?
EARTHQUAKE
(energy waves
are released)
Earthquake
happens at the
TIME of ORIGIN
and waves travel
out FROM FOCUS
Faster P-wave
arrives at the
seismograph FIRST
P-WAVE
ARRIVAL
TIME
Time gap
btw p
and s
Slower s-wave arrives at
the seimograph LATER
S-WAVE
ARRIVAL TIME
If you know
difference in
arrival times, you
can figure out
how far away the
earthquake is!
TAKE A PIECE OF PAPER, AND MARK
OFF THE DIFFERENCE IN ARRIVAL TIME
if gap in time = 04:10
MOVE THE PAPER UNTIL THE TWO
TICK MARKS LINE UP WITH THE P
AND S CURVES
WHEN TICK MARKS LINE UP, GO
STRAIGHT DOWN AND READ THE
EPICENTER DISTANCE
EPICENTER DISTANCE
OF 2800 KM
If the EPICENTER
DISTANCE is 2800 km
from the seismograph,
how long did it take for
the p and s waves to
travel to the station
(TRAVEL TIME)?
EPICENTER DISTANCE
OF 2800 KM
If the p wave
arrived at the
station at 16:00:10,
what was the origin
time of the
earthquake?
EPICENTER DISTANCE
OF 2800 KM
NOW LET’s locate some
earthquakes by
interpreting
seismograms
What’s
triangulation?
TRIANGLE  THREE STATIONS!!!!!
Label the
closest
station
Label the
farthest
station
Determine the
epicenter distance
from each city
Use the data from the
recording stations:
• Station A: San Francisco, California
P-Wave arrival
S-Wave arrival
What is the time
difference
between P and
S wave arrivals?
Use the data from the
recording stations:
• Station B: Denver, Colorado
P-Wave arrival
S-Wave arrival
What is the time
difference
between P and
S wave arrivals?
Use the data from the
recording stations:
• Station C: Missoula, Montana
P-Wave arrival
S-Wave arrival
What is the time
difference
between P and
S wave arrivals?
03:01:00
03:03:00
Difference in arrival times:
San Francisco: 4:10
Denver, Colorado: 3:20
Missoula, Montana: 2:00
1. USE A PIECE OF PAPER TO MARK
OFF THE TIME GAP for that STATION
2. MOVE THE PAPER UNTIL THE
TWO TICK MARKS LINE UP WITH
THE P AND S GRAPHS
3. WHEN TICK MARKS LINE UP,
GO STRAIGHT DOWN AND
READ THE EPICENTER
DISTANCE
4. EPICENTER DISTANCE
OF 2800 KM
EPICENTER DISTANCES
San Francisco: 4:10
2,800 km
Denver, Colorado: 3:20
2,000 km
Missoula, Montana 2:00
1100 km
Where’s the earthquake???
San Francisco:
travel time of 4:10
… is 2,800 km away
from earthquake
5,000
4,000
3,000
2,000
1,000
Open your compass to
the EXACT distance on
the scale.
Once you know distance, you can draw a circle
on the map that shows the possibilities!
.
.
.
Radius from
Missoula = 1100 km
.
.
Radius from
Denver = 2000 km
.
Radius from SanFran =
2800 km
Review of steps to locate
epicenter!!!
Find the difference in arrival times
between p and s waves
Use the ESRT y-axis scale to mark off
the time gap on scrap paper
Match the time gap to p and s waves
curves on ESRT to find distance from the
epicenter on x-axis
Use map scale + compass to draw
circle from seismic station on map
Remember – you need at least 3 seismic
stations to locate the epicenter!